On Tuesday, New Yorkers will go to the polls to vote in a highly tightly contested election that will help determine who will be the next president of the United States.

In this election, we are not just choosing our next president. We are also choosing our commander-in-chief – the person whose responsibility will be to defend our nation at a time of war.

And have no doubt: We are at war.

Our enemy in this struggle is the latest in a long line of totalitarians that Americans have been called on to fight throughout our history: a loose alliance of terrorists and tyrants, bound together by the fanatical ideology of Islamist extremism

Terrorism is the preferred weapon of these Islamist extremists, but it is not their ultimate aim. Their vision is far more ambitious and threatening: a vision of conquest in which huge swaths of the world fall under their vicious and repressive rule.

The Islamist extremists are plotting attacks against us and our allies every day – from the deserts of Iraq to the mountains of Afghanistan, from London and Madrid to Jerusalem and Islamabad – and, if given the chance, right here at home in America.

From the moment the next president steps into the Oval Office, he or she will face life-and-death decisions in this war. That is why we need a president who is going to be ready to be commander-in-chief from day one – a president who won’t need on-the-job training.

And that is why I have decided to cross party lines to endorse Sen. John McCain for president.

I know that it is unusual for someone like me – an Independent Democrat – to support a Republican candidate for president. But the dangers we face as a nation are too profound, and the challenges we face too real, for us to let partisan politics decide who we will support.

After all, the Islamist extremists we are fighting in this war don’t distinguish between Democrats and Republicans. They want to kill all of us, because we are all Americans.

That is why we need a leader who can bring us together again as Americans, and who can rally us to stand in solidarity against our enemies. John McCain is that leader.

When others were silent, John had the courage and the conviction to sound the alarm about the mistakes we were making in Iraq, and to call for more troops and a new strategy there.

And when others waivered, and were fleeing the field of battle, John had the courage and the conviction to stand against public opinion and fight for the surge in Iraq – where, at last, today the forces of Islamist extremism are on the run, and we are winning.

This is the kind of wartime leadership we as a nation desperately need in the years ahead – and it is the kind of leadership that you can expect when John McCain is in White House.

Although security in Iraq has improved dramatically thanks to the surge, this is not a moment for complacency. From terrorist sanctuaries in Pakistan to the resurgent and aggressive nationalism we are witnessing in Russia, to the petroleum-funded extremism of Hugo Chavez in our own hemisphere, the fact remains that we live in a very dangerous world.

Consider the threat posed by the extremist regime in Iran, which continues to sponsor a rogue’s gallery of terrorist proxies across the Middle East and which is zealously working to develop nuclear weapons. Iran is one of the biggest security challenges that the next president is going to face – and there will be no room for error.

Many fine people are running for president this year. But when it comes to keeping our nation safe and solving the problems we face at home, John McCain is the one with the experience, the determination, and the character to lead America forward to a safer, better future.

That is why I hope, next Tuesday, New Yorkers will go to the polls and help make John McCain – a great American patriot – our next great American president.